Delivery of drugs by the buccal route of administration and therapeutic compositions and methods therefor are well known. U.S. Patent No. 4,615,697 to Robinson provides an excellent review of this subject. The buccal delivery systems disclosed in Robinson utilize known bioadhesives to hold the system in place in the buccal cavity after insertion therein. The drug is released from a bioadhesive matrix and absorbed into the buccal lining and provides a means of trans-mucosal delivery of therapeutic agents that are subject to poor bioavailability due to solubility limitations, polarity considerations, degradation due to pH, enzymatic exposure or "first pass" metabolism by the liver or gastrointestinal enzymes after oral ingestion. However, such delivery systems, when used with a backing, have a tendency to distort or curl upon hydration due to the different rates of hydration of the several layers that are present. Also, the drug present is not released into the buccal cavity.
The buccal cavity is susceptible to many ailments which require sustained treatment, however. To that end, it would be desirable to release an active ingredient in the buccal cavity itself for an extended period of time. The present invention provides a means for accomplishing this purpose.